Plant & Animal Genomes XIV Conference

January 14-18, 2006
Town & Country Convention Center
San Diego, CA

Development Of Ryegrass Allele-Specific Markers (GRASP) For Rust Resistance In Lolium perenne

Yongzhong Xing , Britt S Andreasen , Uschi Frei , Thomas Lübberstedt

  Danish Institute of Agricultural Sciences, Dep. of Genetics and Biotechnology, Research Centre Flakkebjerg, 4200 Slagelse, Denmark

GRASP is a EU framework V project involving eight public institutions and one commercial partner. The major target of GRASP is the development of “functional” gene-derived and allele-specific single nucleotide polymorphism markers associated with relevant traits in Lolium perenne such as forage quality, nitrogen use efficiency, disease resistance, and abiotic stress tolerance. More than 100 candidate genes have been isolated for these traits. For each of these candidate genes allele sequences (minimum length 1000 bp per allele) of 20 diverse genotypes (Lolium test set = LTS) are sequenced in order to derive allele-specific SNP markers. Simultaneously, the LTS genotypes have been used to develop synthetic populations under divergent selection for the different traits of interest over two generations. The frequency shift of SNP marker alleles over generations are monitored and used to validate candidate gene – trait associations. At DIAS, 15 expressed disease resistance candidate genes were selected based on sequence homology to other (rust) resistance genes, and mapped into different linkage groups in ryegrass. A few candidate genes were cosegregated with published rust QTL. Allele sequencing for these candidate genes revealed that the SNP frequency in introns was about 3 times higher than in exons. Between 6 and 21 haplotypes were identified among the 20 heterozygous LTS genotypes. Results on linkage disequilibrium in the resistance gene candidates, SNP development, and selection experiments based on two cycles of crown rust infection using a leaf segment test will be presented.